Arguing all the time? This can't be normal.?

Okay, straight to the point. My fiance and I have been together for almost two years. He didn't tell me in the beginning that he and his "best friend", a female had dated for 5 years before just being friends. As soon as I come into the picture, she starts being really shady and I just didn't get a good vibe from her. So we argued. Surely he felt like I was trying to get rid of his friend, but does a real friend start acting out for attention? It was fine before I came around. Anyway they had issues and then it was revealed she had feelings for him. He had to cut her off for the sake of our love and him wanting to marry me. On the other hand she asked if he was really in love with me. A friend? I'm no fool... He did not like how she was interfering and being disrespectful. Over time, he and I have grown closer and when we started to plan for the wedding, I started to see some things I had not seen before. He can be controlling, yet I'm not a woman that can or will be controlled. I will do as I please for the sake of my happiness and contentment. The other thing is that we have clashes because we have two strong personalities and there is not always a compromise. The communication can be way off.. Lately, I've been feeling distant like I just want to walk the heck away! It's so discouraging to argue with someone and they seem so selfish at times. There are more good things than bad, but I can do without the bad because it's enough for me to say BYE! I'm starting to think that perhaps we are just not compatible and it doesn't matter how hard I try. They say change works, but how can I change who I am? I can't You can change things about yourself, but you can't change your genetic makeup and who YOU ARE. If you do then you lose yourself. I guess I'm answering my own question, but if there are any experienced MARRIED people out there OR anyone who can RELATE I'd really appreciate your advice.Should I hold on with just a string of hope? Our age? I'm 25, he's 30.